Bookmark and Share

Notice: On March 31, it was announced that Statalist is moving from an email list to a forum. The old list will shut down at the end of May, and its replacement, statalist.org is already up and running.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

st: Interpreting results from heckprob


From   "Florian Seliger" <florian.seliger@gmx.de>
To   statalist@hsphsun2.harvard.edu
Subject   st: Interpreting results from heckprob
Date   Mon, 27 Jun 2011 14:59:30 +0200

Dear Statalist,

I'm trying to estimate a heckprobit model with CIS data.
The dependent variable in the selection equation is whether a firm has introduced product innovations.
The dependent variable in the outcome equation is whether a firm (that has introduced product innovations) has introduced market novelties.

product innovation yes------->market novelty------>yes
                   no-------->-             ------>no

I'm using a set of control variables such as the log of the number of employees, R&D activities, the proportion of employees with higher education etc., the model variables I'm interested in, and different exclusion restrictions.

The problem is that coefficients of the log number of employees, R&D activities, and the proportion of employees become insignificant in the outcome equation in every specification I have tried out.
Running a simple probit model, all coefficients are highly significant.

My question is:
- How can I interpret this result?
- Do I use the wrong model?

In addition, I would like to ask you if you have an idea which variable (from the CIS survey or additional data) to use as instrument in the selection equation.

Thank you!

Best wishes,
Florian
-- 
NEU: FreePhone - kostenlos mobil telefonieren!			
Jetzt informieren: http://www.gmx.net/de/go/freephone
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2014 StataCorp LP   |   Terms of use   |   Privacy   |   Contact us   |   Site index